为了研究函数的变化规律，往往需要求出不在表上的函数值。因此，我们希望可以根据给定的函数表做一个既能反映函数f(x)的特性，又便于计算的简单函数P(x)。用P(x)近似f(X)。通常选一类简单的函数作为P(x)，并使P(xi)=f(xi)对i=1,2,……,n成立。这样确定下来的P(x)就是我们希望的插值函数，此即为插值法。-To study the changes of function, often need to find the function value is not on the table. We therefore hope that the given function can make a table can reflect the function f (x) features simple and easy to calculate the function P (x). With P (x) is approximately f (X). Usually selected as a function of a class of simple P (x), and P (xi) = f (xi) for i = 1,2, ......, n holds. Such finalized P (x) is the interpolation function we want, that is, for interpolation.